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Collision Spectroscopy in Isomer Characterization: the Case of (E)- and (Z)-p-Nitrophenylazo tert-Buthyl Sulphides
No full textLiquid-liquid extraction procedure for trace determination of cyclophosphamide in human urine by high-performance liquid chromatography tandem mass spectrometry
No full textA sensitive, specific and accurate high performance liquid chromatography/ionspray-tandem mass spectrometry procedure (HPLC/MS/MS) has been developed to quantify cyclophosphamide in human urine from hospital personnel involved in drug preparation and administration of antineoplastic alkylating agents. This methodology, which includes liquid-liquid extraction with ethylacetate, requires no derivatization procedures, preventing cyclophosphamide (CP) from possible thermal and chemical decomposition reactions. We detected the excretion of this unmetabolized alkylating drug in 50% of all the study participants. The amount of CP ranged from 0.1 ng microL-1 to 1.9 ng microL-1 urine. This methodology was validated by the use of ifosfamide as internal standard. The assay was linear over the range 0 to 3.2 ng microL-1 urine, with a lower limit of quantification of 0.2 microL-1. The limit of detection was assessed at 0.05 ng microL-1 urine. This method is characterized by a coefficient of variation < 10%. Standard calibration curves, obtained on three different days, had correlation coefficients always greater than 0.998. The intra and interday precision were within 11%, and accuracy was in the range 99-103%. The mean extracted recovery assessed at three different concentrations (0.5, 0.8, 3.2 ng microL-1) was always more than 85%. The extraction efficiency of cyclophosphamide from urine samples was also studied at six different pH values (pH 4, 5, 6, 7, 8, 10). The maximum extraction efficiency was obtained when the pH of urine solutions was adjusted to 7.
Collision Spectroscopy In Isomer Characterization - the Case of (e)-para-nitrophenyldiazo and (z)-para-nitrophenyldiazo tert-butyl Sulfides
No full textThe structural characterization of the E and Z isomers of p-nitrophenyl-diazo tert-butyl sulphide has been achieved by means of different ionization methods (electron impact, fast atom bombardment, positive-ion chemical ionization) and collision experiments performed under different kinetic energy regimes (high- and low-energy collisions, angle-resolved mass spectrometry and energy-resolved mass spectrometry). The two compounds give rise to identical fragmentation patterns. Collision experiments, both at low energy and in the keV range at a scattering angle of 0-degrees, in M+. species obtained by electron impact on the two isomers, do not show any significant differences; the same experiments performed with 8 keV ions at a scattering angle of 2-degrees indicate a clear difference in the absolute abundances of the two main daughter ions. High-energy collisions of MH+ ions obtained by fast atom bombardment lead to different spectra at both 0-degrees and 2-degrees scattering angles, proving that the energy deposition in the preselected species is an important parameter. Low-energy collisions with argon of MH+ ions generated by positive-ion chemical ionization (NH4+) give rise to almost identical energy-resolved mass spectra, whereas the same experiments using helium as target gas lead to a clear distinction between the two isomers
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Application of high performance liquid chromatography/tandem mass spectrometry in the environmental and biological monitoring of health care personnel occupationally exposed to cyclophosphamide and ifosfamide
No full textTwenty four workers (10 involved in the preparation and 14 in administration) exposed to cyclophosphamide (CP) and ifosfamide (IF) in two Italian hospitals were monitored. The extent of exposure was assessed by the analysis of air samples, wipe samples, pads and gloves. Urinary excretion at the beginning and at the end of the work shift was also measured by liquid-liquid extraction and analysis by high performance liquid chromatography/tandem mass spectrometry. Three out of 24 air samples were positive for CP or IF. In wipe samples, CP concentrations ranging from < 0.001 to 82.4 micrograms/dm2 in Hospital A (32 samples) and from 0.2 to 383.3 micrograms/dm2 in Hospital B (17 samples), were found. IF concentrations varied from < 0.001 to 90.9 micrograms/dm2 in Hospital A and from 0.01 to 141.5 micrograms/dm2 in Hospital B. Pads (from 11 to 13 for each operator) were contaminated with CP and IF especially on arms, legs and chest. The use of a plastic-backed liner on the working tray in the laminar flow hoods was demonstrated to compromise the containment properties of the hood. Urine samples were positive for CP in 50% of the workers (range: 0.1-2.1 micrograms/L), whereas IF was detected in 2 subjects only (range: 0.1-0.8 microgram/L). The results of this investigation demonstrate that vertical laminar airflow hoods, when incorrectly used, might represent a source of contamination and that higher risk may depend on lack of educational programmes and observance of preventive guidelines
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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